The surfaces of the respiratory tract present the first potential reaction sites for air pollutants in inhaled air. Previous studies have examined the effects of air pollutants on these surfaces, particularly the alveolar region, either in vivo followed by sample workup, or using model systems. We propose to study the chemical nature of the surfaces of rat lungs directly, and the changes caused by air pollutants such as NO2 and O3, using Fourier transform infrared spectroscopy (FT-IR) combined with surface reflectance techinques. The alveolar region with its pulmonary surfactant layer will be emphasized. The PI's experience with these sophisticated spectroscopic techniques in determining gas phase kinetics and mechanisms will be expanded on the biomedical side through a collaborative interaction with the Air Pollution Health Effects Laboratory at the University of California, Irvine. Specific aims and methodologies of the proposed research are as follows: (1) to the infrared (IR) spectra of model systems of lipids and phospholipids adsorbed on silica gel, and the changes induced by exposure to the gaseous air pollutants NO2 and O3 singly or in combination, using techniques (DRIFTS) for obtaining the spectra of surfaces; (2) to obtain the IR absorption spectrum of the surface of the alveolar region of rat lungs and of mucus lining the trachea, using DRIFTS and ATR, or a new technique (CIR) for obtaining spectra of samples with high water content; (3) to monitor changes in the spectra of the lung surfaces on exposure to ppm levels of NO2 and O3 in air, either singly or in combination; (4) to compare the spectra in (3) with those from rats exposed to these air pollutants in vivo; (5) to obtain samples of pulmonary surfactant from rats using conventional lavage techniques and compare the IR spectrum to that of the alveolar region recorded using surface reflectance. From a comparison of the results from model systems, rat lung surfaces and lavage fluids, the mechanism of action of these air pollutants on lung surfaces at a molecular level will be established. All major spectroscopic equipment needed is on hand in the PI's laboratory. Animal exposures will be carried out at the University of California, Irvine, nearby.